The arrangement can be used when supplying light emitting diodes, abbreviated to LEDs, such as are used for instance in portable telephones and digital cameras.
Voltage converters, referred to as direct current/direct current converter, abbreviated to DC/DC converter, usually serve to convert a low voltage into a higher voltage. The ratio of the output voltage to the input voltage can often be established by choosing a multiplication factor. Voltage converters are employed for example in generating flashes with an LED and the backlighting of a display.
Portable devices are usually operated using a battery and therefore do not have a constant voltage for the electrical load to be supplied, such as an LED, for instance. However, the function of the load should not be influenced by a decreasing input voltage. For this reason, it is possible to operate voltage converters with an additional circuit for setting the multiplication factor.
If a plurality of LEDs of different types or with manufacturing tolerances are operated in parallel, the situation can occur in which the multiplication factor has to be increased in order to be able to operate an LED with a high threshold voltage. This results in an impaired efficiency of the overall arrangement.